This invention relates to the chlorination of titaniferous materials using a special porous carbon reductant.
Titaniferous materials are often subjected to chlorination as chlorination is an efficient and economical way to obtain a high purity source of titanium for making titanium alloys, titanium compounds, and especially pigmentary titanium dioxide. Several processes have been described in the art for the chlorination of titaniferous materials. Such processes generally react a titanium-containing raw material such as rutile ore or ilmenite ore, with a chlorine-providing material and a carbon reductant at an elevated temperature according to one or both of the following equations: EQU TiO.sub.2 +2Cl.sub.2 (g)+C(s).fwdarw.TiCl.sub.4 (g)+CO.sub.2 (g) EQU TiO.sub.2 +2Cl.sub.2 (g)+2C(s).fwdarw.TiCl.sub.4 (g)+2CO(g)
Conventional chlorination reactions are generally carried out at about 1000.degree. C., but can be carried out at any temperature in the range from about 800.degree. C. to about 2000.degree. C., using various conventional carbon reductants and chlorine sources.
The chlorination reactions can be carried out in a variety of reaction zone configurations. Fixed-bed, fluidized-bed, and flow reaction zones have been utilized. Each type of reaction zone has known advantages and disadvantages; however, the fluid-bed reaction zone is by far the preferred type for commercial processes. A key disadvantage of the flow processes has been that the chlorination reactions proceed at a relatively slow rate under most conveniently achieved reaction conditions and therefore an extremely long reaction chamber is required to provide the necessary residence time for the reactants within the chamber and a large excess of ore is required to cause the chlorine to react substantially completely.
It has now been found that a flow process for the chlorination of titaniferous materials can be accomplished within a reaction zone of reasonable size in an efficient fashion if the carbonaceous reductant utilized is a porous carbon having micropores with a pore diameter of less than about 20 A.
One embodiment of the present invention is to chlorinate powdered titanium-containing materials and ores in a down-flow chlorination reaction zone wherein powdered porous carbon reductant and the titanium-containing material are entrained in a stream of down-flowing chlorine-providing gas. The chlorination reactions proceed substantially to completion as the material falls through the reaction chamber.
Another process is to chlorinate titanium- and iron-containing materials and ores to produce titanium chlorides and by-product metallic iron in a laminar-flow process. According to this process, the stoichiometry of the reactants is controlled along with the reaction temperature and the flows of the process are designed to prevent any back mixing within the reaction chamber, thus a metallic iron by-product is produced instead of the conventionally produced iron chloride by-product.
It is an object and advantage of the present process that it utilizes a flow of reactants rather than a fixed or a fluidized bed.
It is a further object of the present invention that powdered raw materials instead of granular raw materials can be utilized in the present process, such powdered materials being readily available and largely commercially overlooked because of the expense of processing. A further object and advantage of the present invention is that reaction times and reaction rates are greatly enhanced, thus allowing for the use of smaller reaction zones for the above-described flow processes.
These and other objects and advantages of the present invention will become more apparent from the detailed description of the invention.